Hot water tanks are in widespread use in both residential and commercial installations. Typically, these tanks include a heating element located at the bottom of the tank, with a hot water outlet pipe and a make-up water inlet pipe connected through the top of the tank. The tanks generally include a thermostat for setting the desired temperature of the hot water withdrawn from the tank, and typically include a blow-out outlet connected through a pressure relief valve to allow hot air, steam and hot water to be removed from the tank through the relief valve when the pressure exceeds the setting of the relief valve. This is done to prevent catastrophic explosions of the hot water tank from taking place.
The pressure relief valve may be periodically operated for relatively short intervals during the normal operation of the hot water tank. This allows bubbling steam and water to pass through the relief valve for discharge. Once the pressure drops below the setting of the relief valve, it turns off and normal operation of the hot water tank resumes. After a period of time, however, mineral deposit buildup and corrosion frequently take place in the relief valve, as a result of these periodic operations. In time, such corrosion or scale build up may impair the operation of the relief valve, so that it no longer responds to the operating pressure and fails to open. When this occurs, the possibility of a catastrophic explosion of the hot water tank exists. In actuality, such explosions do occur, and they can cause substantial damage to the structure in which the hot water tank is located.
In addition to the possibility of high pressure explosions taking place in a hot water tank, other conditions, which also can lead to significant damage to the structure in which the hot water tank is placed, can occur. As hot water tanks age, frequently they develop leaks, or leaks develop in the water inlet pipe or hot water outlet pipe to the tank. If such leaks go undetected, water damage from the leak to the surrounding building structure results.
Two United States patents, Franklin U.S. Pat. No. 5,240,022 and Barron U.S. Pat. No. 5,428,347 disclose sensor systems, utilized in conjunction with hot water tanks designed to shut off the water supply in response to the detection of water leaks. In addition, these patents include multiple parallel operated sensors, operating through an electronic control system, to either turn off the main water supply or individual water supplies to different appliances, such as the hot water heater tank.
The United States patent to Fulton U.S. Pat. No. 3,154,248 discloses a temperature control relief valve operating in conjunction with a overheating/pressure relief sensor to remove or disconnect the heat source from a hot water tank when excess temperature is sensed. The temperature sensor of Cargill is designed to be either the primary control or a backup control with the pressure relief valve.
Three other United States patents, to Lenoir U.S. Pat. No. 5,632,302; Salvucci U.S. Pat. No. 6,084,520; and Zeke U.S. Pat. No. 6,276,309, all disclose safety systems for use in conjunction with a hot water tank. The systems of these patents all include sensors which operate in response to leaked water to close the water supply valve to the hot water tank. The systems disclosed in the Salvucci and Zeke patents also employ the sensing of leaked water to shut off either the gas supply or the electrical supply to the hot water tank, thereby removing the heat source as well as the supply water to the hot water tank.
The United States patent to Patton U.S. Pat. No. 3,961,156 utilizes sensing of the operation of the standard pressure relief valve of a hot water tank to also operate a micro switch to break the circuit to the heating element of the hot water tank.
While the various systems disclosed in the prior art patents discussed above function to sense potential malfunctioning of a hot water tank to either turn off the water supply, the energy supply, or both, to prevent further damage, none of the systems disclosed in these patents are directed to a safety system for monitoring potentially damaging pressure increases in the hot water tank in the event that the pressure relief valve malfunctions. This potential condition, however, is one which is capable of producing catastrophic damage to the structure in the vicinity of the hot water tank.
It is desirable to provide a tank monitoring system which overcomes the disadvantages :of the prior art, which is capable of monitoring one or more potential failure parameters of a hot water tank, and which may be installed as an after market add on, or which may be incorporated into original equipment hot water tanks, and which further includes the capability of remote monitoring of the hot water tank.
It is an object of this :.invention to provide an improved hot water tank monitoring system.
It is another object of this invention to provide an improved hot water tank monitoring system which turns off the water supply and the energy supply to a hot water tank upon the sensing of one or more parameters of operation of the hot water tank.
It is an additional object of this invention to provide an improved hot water tank monitoring system for sensing excess pressure in the hot water tank to shut off the water supply to the tank and to shut off the energy supply to the heating unit of the tank.
It is a further object of this invention to provide a tank monitoring system for a hot water tank including a pressure sensor located to sense the pressure variations of the tank without water flow through the pressure sensor to provide an output for shutting off the water supply and/or the energy supply to the heating unit of the hot water tank when excess pressure is sensed.
In accordance with a preferred embodiment of the invention, a monitoring system for a hot water tank having an input water supply, an output water line and a source of heat energy is provided. The system includes a pressure sensor connected to sense the pressure inside the tank and provide an output signal when the sensed pressure exceeds a predetermined threshold. Additional sensors also may be provided to respond to one or more additional operating parameters of the tank, including excess temperature, water level, and water leaks to provide additional output signals whenever a sensed parameter reaches a predetermined threshold. A normally open shut off valve is located in the input water supply; and a control for disconnecting the source of heat energy from the hot water tank also is provided. A controller is coupled to receive output signals from the pressure sensor, and the additional parameter sensors, if any, and operates in response to an output signal from a sensor to close the shut off valve in the water supply line, and to cause the source of heat energy to be disconnected from the hot water tank.